Radio frequency beam management and failure pre-emption

ABSTRACT

A processor in a UE evaluates a radio frequency beam quality metric against a threshold, switches from a first beam to a second beam in response to determining the metric falls below the threshold, and transmits to a base station (BS) a report that includes beam measurements. The report indicates the UE has performed the switching and that the beam measurements are with respect to the second beam. A processor in a UE/BS associates narrower and broader beams, uses the narrower beam, rather than the broader beam, to transfer user data between the BS and the UE, evaluates a beam quality metric of the narrower beam against the threshold, and switches to using the broader beam, rather than the narrower beam, to transfer user data between the BS and the UE in response to determining the beam quality metric of the narrower beam falls below the threshold.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims priority based on U.S. Provisional Application,Ser. No. 62/544,719, filed Aug. 11, 2017, entitled BEAM MANAGEMENT FORMMWAVE IN NEW RADIO, which is hereby incorporated by reference in itsentirety.

This application is related to the following U.S. Non-Provisionalapplications, each of which is hereby incorporated by reference in itsentirety.

Serial No. (Docket No.) Filing Date Title 15/855,148 Dec. 27, 2017COMMON PHASE ERROR (CPE) (NATI.018) COMPENSATION FOR FREQUENCY DIVISIONMULTIPLEX (FDM) SYMBOLS IN WIRELESS COMMUNICATION SYSTEMS 15/940,103Mar. 29, 2018 WIRELESS COMMUNICATION (NATI.019) SYSTEM THAT PERFORMSMEASUREMENT BASED SELECTION OF PHASE TRACKING REFERENCE SIGNAL (PTRS)PORTS 15/969,883 May 3, 2018 WIRELESS COMMUNICATION (NATI.020) SYSTEMTHAT PERFORMS BEAM MANAGEMENT USING NESTED REFERENCE SIGNALS 15/969,923May 3, 2018 WIRELESS COMMUNICATION (NATI.030) SYSTEM THAT PERFORMS BEAMREPORTING BASED ON A COMBINATION OF REFERENCE SIGNAL RECEIVE POWER ANDCHANNEL STATE INFORMATION METRICS TBD concurrently RADIO FREQUENCY BEAM(NATI.026) herewith MANAGEMENT AND RECOVERY

BACKGROUND

The disclosed embodiments relate to mobile telecommunications.

The New Radio (NR) definition in 3GPP (3^(rd) Generation PartnershipProject) for mobile systems will encompass a variety of deploymentscenarios envisioned for 5G (fifth generation) mobile communicationsystems. MIMO (multiple input, multiple output) communication systemscan be used for 5G TDD (time division duplex) air interfaces. Flexible(scalable) frame structures are being considered for block symboltransmissions within the new 5G cellular communication standardincluding various frame structure parameters such as FFT (fast Fouriertransform) size, sample rate, and subframe length. Beam basedtransmission schemes can be used for directional 5G communication links.

FIG. 1 (Prior Art) is a diagram of an example embodiment including abase station 102 with M antennas 104 that provides a wireless MIMOcommunication system 100. The MIMO base station 102 communicates throughits M antennas 104 with K different user equipment (UE) devices 106,such as mobile handsets, having one or more antennas 108. Spectralefficiency is improved by using massive MIMO communication systemshaving base stations with relatively large numbers of antennas. Exampleembodiments for massive MIMO communication systems are described withinU.S. Published Patent Application 2015/0326286, entitled “MASSIVE MIMOARCHITECTURE,” U.S. Published Patent Application 2015/0326383, entitled“SYNCHRONIZATION OF LARGE ANTENNA COUNT SYSTEMS,” and U.S. PublishedPatent Application 2015/0326291, entitled “SIGNALING AND FRAME STRUCTUREFOR MASSIVE MIMO CELLULAR TELECOMMUNICATION SYSTEMS,” each of which ishereby incorporated by reference in its entirety.

BRIEF SUMMARY

In one aspect the present invention provides a user equipment (UE) forperforming radio frequency beam management in communication with a basestation. The UE includes a processor and a memory that stores athreshold. The processor evaluates a beam quality metric against thethreshold, switches from a first beam to a second beam in response todetermining the beam quality metric falls below the threshold, andtransmits to the base station a report that includes beam measurements.The report indicates the UE has performed the switching and that thebeam measurements are with respect to the second beam.

In another aspect, the present invention provides a method forperforming radio frequency beam management in communication between abase station and a user equipment (UE). The method includes the UEevaluating a beam quality metric against a threshold, switching from afirst beam to a second beam in response to determining the beam qualitymetric falls below the threshold, and transmitting to the base station areport that includes beam measurements. The report indicates the UE hasperformed said switching and that the beam measurements are with respectto the second beam.

In yet another aspect, the present invention provides a base station(BS)/user equipment (UE) attempting to pre-empt radio frequency beamfailure in communication between a UE/BS. The BS/UE includes a processorand a memory that stores a threshold. The processor associates narrowerand broader beams between the BS and the UE, uses the narrower beam,rather than the broader beam, to transfer user data between the BS andthe UE, evaluates a beam quality metric of the narrower beam against thethreshold, and switches to using the broader beam, rather than thenarrower beam, to transfer user data between the BS and the UE inresponse to determining the beam quality metric of the narrower beamfalls below the threshold.

In yet another aspect, the present invention provides a method forattempting to pre-empt radio frequency beam failure in communicationbetween a base station (BS) and a user equipment (UE). The methodincludes associating narrower and broader beams between the BS and theUE, using the narrower beam, rather than the broader beam, to transferuser data between the BS and the UE, evaluating a beam quality metric ofthe narrower beam against a threshold, and switching to using thebroader beam, rather than the narrower beam, to transfer user databetween the BS and the UE in response to determining the beam qualitymetric of the narrower beam falls below the threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

It is noted that the appended drawings illustrate only exemplaryembodiments and are, therefore, not to be considered limiting of thescope of the present inventions, for the inventions may admit to otherequally effective embodiments.

FIG. 1 (Prior Art) is a diagram of an example embodiment including abase station with M antennas that provides a wireless beam formed MIMOcommunication system.

FIGS. 2A-B are diagrams that provide example embodiments for selectionof wide beam and narrow beam reference signals, respectively.

FIGS. 3A-B are diagrams that provide example embodiments for narrow beamreference signals that correspond to different wide beam referencesignals.

FIG. 4 is a flowchart that provides an example embodiment where a UEreports its computational capabilities and the base station (e.g.,gNodeB (gNB)) uses this information to configure beam reporting and theUE performs beam measurement and reporting based on this configuration.

FIG. 5 is a block diagram of an example embodiment for a wirelesscommunication system that can use the disclosed techniques.

FIG. 6 is a diagram of an example embodiment for electronic componentsthat can be used to implement a base station and/or user equipment (UE)for the disclosed embodiments.

FIGS. 7-9 are block diagrams that provide example embodiments fordifferent implementations where clock signals and related circuitry areused as LOs for RF channels within downlink (DL) and/or uplink (UL)circuitry for base stations or UEs.

FIG. 10 is a diagram that provides an example diagram of two framestransmitted from a MIMO base station that include two orthogonal PTRSports with the PDSCH.

FIGS. 11A-C is a flow diagram that provides an example for performingthe PN correlation at the UEs and for the feedback of these correlationsfrom the UE to the base station.

FIG. 12 is a block diagram of an example embodiment for circuitry thatcan be used to provide a baseband receiver, a baseband transmitter,multi-FPGA processing circuitry, and a real-time processor with respectto the embodiment of FIG. 5.

FIG. 13 is a block diagram of an example embodiment for symbolprocessing for OFDM transmissions including blind CPE estimation for CPEcompensation.

FIG. 14 is a block diagram of an example embodiment where the CPEestimator includes multiple estimation algorithms including a pilot onlyCPE estimation algorithm, a blind only CPE estimation algorithm, and apilot aided blind CPE estimation algorithm.

FIG. 15 is a diagram illustrating interplay of beam management, beamrecovery and radio link failure.

FIG. 16 is a diagram illustrating beam management and beam recovery.

FIG. 17 (collectively FIGS. 17A and 17B) is a signal diagramillustrating a UE-initiated beam management method.

FIG. 18 (collectively FIGS. 18A and 18B) is a signal diagramillustrating a gNB-initiated beam management method.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed embodiments provide systems and methods for nestedreference signal (RS) designs for beam management in wirelesscommunications systems. The proposed embodiments can include, forexample, one or more of the following:

1. Construction of the beam set of reference signals (RSs) such that theRSs used for coarse beam selection are linked to the RSs used for finebeam selection in a unique manner. For one example embodiment for NRsolutions, SS (Synchronization Signals) and/or wide beam CSI-RS (ChannelState Information-Reference Signal) are used for coarse beam selection,and narrow beam CSI-RS are used for fine beam selection.2. Indication of the linkage between the selected coarse beam RSs andfine beam RSs is used by the UE (user equipment), and further linkage tothe PDCCH (physical downlink control channel) and PDSCH (physicaldownlink shared channel) beams is also used. For one example embodiment,this linkage indication is performed via signaling of quasi co-location(QCL) assumptions. For one further example embodiment, this is done viaimplicit indication to the UE from the base station such as a gNB(gNodeB) in the NR definition.3. Beam reporting is implemented based upon a combination of RSRP(reference signal receive power) and CSI (channel state information)metrics. For one example embodiment, this beam reporting can include aUE reporting its CSI computation capability to the base station (e.g.,gNB).

-   -   Other variations can also be implemented while still taking        advantage of the techniques described herein.

It is noted that for certain wireless MIMO communication systems such asNR implementations, SS (synchronization signal) blocks are used. The SSis transmitted in a beam-sweeping manner over a narrow bandwidth withrespect to legacy omni-directional/sectoral LTE beams, although thebandwidth of the SS may be wide relative to narrow beam CSI-RS. Theperiodicity of this beam sweep is called an SS burst set. The typicalorder of this periodicity is tens of milliseconds. While the primarypurpose of the SS is for initial access, SS can be used for beammanagement in CONNECTED state UEs also. The SS acts as an always “on”and cell wide signal. The beam set represents the SS beams selected bythe gNB (gNodeB) or other base station so that it can finish sweepingall of the available beam directions in a reasonably small number ofbeams and in a relatively small amount of time to reduce the beamselection and initial access latency. In order to do this, the beamseither can be narrow beams where only a subset of all available narrowbeams are sampled or can be wider beams that fully cover all availablenarrow beam directions. Beam reporting is the reporting of the measuredbeam metrics by the UE back to the gNB. This beam reporting is used bygNB to assign a beam to the UE. The simplest and most common metric isbeam RSRP (Reference Signal Receive Power). This is simply the receivepower of the RS over a certain receive BW (bandwidth).

Embodiments for nested reference signal (RS) designs for beam managementin wireless communications systems will now be described in more detail.

Construction of Beam Sets Linking Coarse Beam Selection to Fine BeamSelection

For one example embodiment, construction of the beam set of referencesignals (RS) is performed such that the RS used for coarse beamselection is linked to the RS used for fine beam selection in a uniquemanner. For this embodiment, the TX (transmit) beam selection happensthrough a two stage process.

For Stage 1, a coarse beam is selected via beam sweeping. (Thiscorresponds to the P1 procedure as defined in NR.) For Stage 2 after thecoarse beam direction has been found, the beam direction is refined tofind the fine beam. This fine beam will then be used for furthertransmissions to the UE in the PDCCH and PDSCH beams. (This correspondsto the P2 procedure as defined in NR.)

In order to aid the coarse-to-fine beam selection, it is proposed toconstruct the RS that is used such that there is a nested structure ofthe RS beams. More specifically, it is proposed that either the widebeam SS or the wide beam CSI-RS is used as the RS for the coarse beams,and the narrow beam CSI-RS is used as the RS for the fine beams. It isnoted, however, that other options are not precluded and could still beused.

For one example embodiment, the beam set is constructed as follows:

-   -   First, the N different wide beam RSs are designed such that they        will cover the entire beam sweeping area of interest.    -   Then, for the n^(th) wide beam RS, M different fine beam RSs are        designed such that the beam direction of the fine beam RS is        subsumed (covered) by the n^(th) wide beam RS. Here n is a        particular instance of the wide beam RS and can be from 1 up to        N, and the total number of fine beam RS can be N times M. In        other words, if the UE receives one of these M fine beam RSs as        its strongest measured fine beam RS, then it will also        correspondingly select the n^(th) wide beam RS as its strongest        measured wide beam RS. In this example embodiment, all wide        beams have the same number of narrow beams. The method is not        limited to this example but each wide beam can have a different        number of narrow beams. It is also noted the “M” and “N” are        positive integers for this embodiment.

FIGS. 2A-B and FIGS. 3A-B provide example embodiments for thiscoarse-to-fine beam selection. Looking first to FIG. 2A, wide beam RSsare provided by a TRP (transmit/receive point) 192 with antenna 194using N different SSs, denoted SS(1), SS(2) through SS(N). For FIG. 2B,eight (8) different fine beam RSs are provided by a TRP 192 usingCSI-RSs, denoted CSI-RS(1), CSI-RS(2) through CSI-RS(8). In FIG. 3A,CSI-RS numbers 1-4 correspond to one of the SS beams, namely SS beamnumber 1, SS(1). In FIG. 3B, CSI-RS numbers 5-8 correspond to one of theSS beams, namely SS beam number 2, SS(2). The various beams are receivedby a UE 196 having antenna 198.

Indication of Linkage to UE and Further Linkage to PDCCH/PDSCH Beams

For one example embodiment, indication of the linkage between the coarseand fine beam selection RS is provided to the UE, and further linkage tothe PDCCH and PDSCH beams is used. As seen above, the linkage is uniquebetween the coarse and fine beam selection RSs. However, the UE does notknow this linkage a priori. A method is proposed to indicate thislinkage information to the UE.

The UE knows the SS beam number and direction as it is periodicallytransmitted in a known manner for NR implementations. This periodicityas well as the manner of transmission can be deduced by the UE byreceiving the System Information (SI) broadcast in the SS blocks (e.g.,in the PBCH (physical broadcast channel) part of the SS block). TheCSI-RS beams, however, are not known to the UE. These can be UE specificor UE Group specific or cell specific. Without prior knowledge aboutthese CSI-RS beams, the UE cannot determine how they correspond to theSS beam.

The following implicit linkage and/or explicit linkage techniques can beused for this linkage although other methods could also be used.

-   -   Implicit Linkage via Nesting Structure Design—Linkage can be        implicitly indicated via nesting structure design. Each Beam        Pairing between the TRP and UE, which is also called a Beam Pair        Link (BPL), is expected to have a unique BPL tag/identifier        (ID). The tag/ID of each beam is designed to encode in it the        nesting structure, and the SS beam identifier that it        corresponds to. As an example, there can be twenty (20) SS beams        each corresponding to a unique symbol or slot within a SS burst        set periodicity. Each SS beam will have a set of BPL tags/IDs        and one out of that set is allotted to a CSI-RS that is linked        to that SS beam. One alternative method to encode this implicit        linkage is to use the choice of CSI-RS sequences. The set of        CSI-RS sequences is initialized or chosen based on the SS beam        that the CSI-RS beam corresponds to. In this manner there is        implicit indication of the coarse and fine beams.    -   Explicit Linkage via CSI-RS Configuration—Linkage can be        explicitly indicated via CSI-RS configuration. In this option,        the linkage of CSI-RS beam to SS beam is indicated using an        explicit signaling of a QCL (quasi co-location) assumption        between the coarse and fine beams. This QCL will be a quasi        co-location of only the spatial parameters of the two beams. For        each CSI-RS that is configured for the UE in either UE specific        or UE Group specific or cell specific, the spatial QCL with one        of the coarse beam (SS) is indicated as part of the CSI-RS        configuration message.

In one embodiment, the linkage is one of a set of possible linkages maybe configured to the UE as a Transmission Configuration Indication (TCI)state parameter (TCI-States). Each configured TCI state may include onereference signal (RS) set TCI-RS-SetConfig. Each TCI-RS-SetConfig maycontain parameters for configuring a QCL relationship between thereference signals in the RS set and the demodulation reference signal(DM-RS) port group of the physical downlink shared channel (PDSCH)between the BS and UE. The QCL-TypeD may be used to indicate the QCLrelationship with respect to spatial receive parameter between the twoRS.

In one embodiment, the linkage may be indicated to the UE in thedownlink control information (DCI) message for the UE when the UE isconfigured with a higher layer parameter TCI-PresentInDCI that is set asenabled for the Control Resource Set (CORESET) scheduling a PDSCHbetween the BS and UE. CORESET is the set of resource elements in whicha physical downlink control channel (PDCCH) can be sent to the UE.

Beam Reporting Based on a Combination of RSRP and CSI Metrics

For further embodiments, the CSI metric of one or more beams can also bereported by the UE to the gNB during the beam management procedure. ThisCSI metric will be in addition to the RSRP metric reported for thebeams. The CSI report includes one or more of Channel QualityInformation (CQI), Rank Information (RI), Precoder Matrix Information(PMI), and/or other reported information.

It is noted that it can be computationally intensive for a UE to computethe CSI metric for each beam. Further for the NR standard, UEs also fallwithin differing categories where the category of the UE corresponds toits target application and is predefined in the NR standard. Dependingon the UE category, the UE may have a differing ability to computemultiple CSIs as the beam selection metric.

To address this potential issue for certain embodiments, each UE isconfigured to indicate its CSI computation capabilities to the gNB, andthe gNB then takes these capability reports into account and configuresthe UE to report a specific number of CSIs in every beam reportinginstance. The UE capability report can be hard coded into the UECategory which is fixed for a given UE. Or, the UE computationcapability can be indicated during UE initial access process by the UEto the gNB in a dynamic manner. Further, as such beam management isenvisioned to be required primarily above 6 GHz operation, compatibilitywith sub 6 GHz operation of NR is ensured. Hence, the UE may determinewhether or not the computation capability indication is supported viathe system configuration contained in the System Information that isbroadcast by the gNB. Further, the UE may compute the additional CSIseach time it does a beam measurement as part of a beam managementprocedure. It is noted that in this method, the CSI is computed,reported and used for the purposes of beam selection only. Also, the gNBscheduler will take into account the reported Ranks and CQIs of multiplebeams to make the final selection on the beam that the UE will beconfigured with for further data and control channel transmissions. Thiswill be supplemental information to the scheduler, which is in additionto the RSRP measurements that the scheduler will have for these and/ormore beams.

FIG. 4 provides an example embodiment 400 where a UE reports itscomputational capabilities and the base station (gNB) uses thisinformation to configure beam reporting. In block 402, the UE reportsits CSI computation capability to the gNB. In block 404, the gNBconfigures the UE to compute and report CSIs every beam sweep. In block406, the UE computes RSRP of all beams in the beam sweep, which are partof the P1/P2 procedure in NR. In block 408, the UE selects the top Ynumber of beams sorted by their RSRP. In block 410, the UE selects thetop X number of beams sorted by their RSRP (X≤Y). In block 412, for theselected X beams, UE computes the CSI. In block 414, the UE reports theRSRP of the Y beams and all or part of the CSI of the X beams. It isnoted the “X” and “Y” are positive integers for this embodiment. It isalso noted that different and/or additional process steps could also beincluded while still taking advantage of the techniques describedherein.

In one embodiment, the UE may perform physical layer (Layer 1)processing that is UE implementation-specific. The physical layerprocessing may include physical layer filtering. In one embodiment, theUE may perform network layer (Layer 3) processing configured to the UEvia Radio Resource Control (RRC) configuration. The network layerprocessing may include network layer filtering.

It is noted that the disclosed embodiments can be used with respect to avariety of OFDM-based transmission schemes for RF communication systems.It is also noted that as used herein, a “radio frequency” or RFcommunications means an electrical and/or electro-magnetic signalconveying useful information and having a frequency from about 3kilohertz (kHz) to thousands of gigahertz (GHz) regardless of the mediumthrough which such signal is conveyed. The OFDM-based transmissions maybe transmitted through a variety of mediums (e.g., air, free space,coaxial cable, optical fibers, copper wire, metal layers, and/or otherRF transmission mediums). As one example, the disclosed embodimentscould be used millimeter (mm) wave transmissions between 30-300 GHzhaving wavelengths of 1-10 mm (e.g., a transmission range of 71-76 GHz)if OFDM-based modulation were used for the mm wave transmissions. Inaddition, the disclosed embodiments will likely be useful for 5Gsolutions up to 40 GHz where OFDM-based modulations are more likely tobe implemented. For example, 5G frequency ranges and bands around 28GHz, 39 GHz, and/or other frequency ranges or bands where OFDM-basedmodulation is used for RF transmissions will benefit from the disclosedtechniques. It is further noted that example wireless communicationsystems within which the disclosed techniques can be applied are alsodescribed in U.S. Published Patent Application No. 2015-0303936 (Ser.No. 14/257,944) and U.S. Published Patent Application No. 2015-0305029(Ser. No. 14/691,339), each of which is hereby incorporated by referencein its entirety.

FIG. 5 is a block diagram of an example embodiment for a communicationsystem 700 that can transmit and receive OFDM symbols as describedherein. The example embodiment of FIG. 5 includes a transmit path and areceive path. The transmit path includes multi-FPGA processing circuitry702, a baseband transmitter 704, an IF upconverter 706, and an RFtransmitter 708. The receive path includes an RF receiver 712, an IFdownconverter 714, a baseband receiver 716, and multi-FGPA processingcircuitry 718. The transmit path and the receive path that arecommunicating with each other can be located in different devices (e.g.,base station and user equipment for cellular communications). Ifbi-directional communications are desired, the different devices caneach include a transmit path and a receive path. Other variations canalso be implemented.

Looking to the transmit path, transmit data 722 is sent to multipleFPGAs 702 that provide multi-FPGA processing of the transmit data 722.The transmit data 722 can be generated by other processing circuitrysuch as a control processor or other circuitry. These FPGAs 702 canoperate at a selected clock rate (e.g., 192 MS/s (mega samples persecond) or other rate) and can use efficient parallel wide data pathimplementations, for example, with multiple (e.g. 16) data elements(e.g., baseband samples) per wide data path sample. The FPGAs 702 outputdigital baseband signals 724 to the baseband transmitter 704. Thebaseband transmitter 704 includes a digital-to-analog converter (DAC)that converts the digital baseband samples to analog baseband signals726. The baseband transmitter 704 including the DAC can operate at aselected sampling rate (e.g., 3.072 GS/s (Giga samples per second) orother rate) and can receive digital baseband samples from one ormultiple FPGAs 702 within the multi-FPGA processing circuitry. Theanalog baseband signals 726 are received by an IF (intermediatefrequency) upconverter 706 that mixes the analog baseband signals 726 tohigher frequency IF signals 728. These IF signals 728 are received bythe RF transmitter 708 which further upconverts these signals to thefrequency range of the desired transmissions.

Looking to the receive path, the receiver 712 receives the RFtransmissions from the RF transmitter which can be within a desiredfrequency range. The RF receiver 712 downconverts these RF transmissionsto lower frequency IF signals 732. The IF signals 732 are then receivedby an IF downconverter 714 that mixes the IF signals 732 down to analogbaseband signals 734. The analog baseband signals 723 are then receivedby a baseband receiver 716. The baseband receiver 716 includes ananalog-to-digital converter (ADC) that converts the analog basebandsignals 734 to digital baseband signals 736. The baseband receiver 716including the ADC can operate at a sampling rate (e.g., 3.072 GS/s (Gigasamples per second) or other rate) and can send digital baseband samples736 to one or multiple FPGAs within the multi-FPGA processing circuitry718. The FPGAs 718 receive the digital baseband signals 736 and generatedigital data that can be processed by additional processing circuitrysuch as a control processor or other circuitry. These FPGAs 718 canoperate at a selected rate (e.g., 192 MS/s (mega samples per second) orother rate using efficient parallel wide data path implementations, forexample, with multiple (e.g., 16) data elements (e.g., baseband samples)per wide data path sample.

The disclosed embodiments can also be used for OFDM-based transmissionschemes for massive MIMO cellular telecommunication systems as describedin U.S. Published Patent Application 2015/0326291, entitled “SIGNALINGAND FRAME STRUCTURE FOR MASSIVE MIMO CELLULAR TELECOMMUNICATIONSYSTEMS,” which is hereby incorporated by reference in its entirety.Such massive MIMO (multiple input, multiple output) communicationsystems can be used for 5G dynamic TDD (time division duplex) airinterfaces. The 5G (5^(th) generation) mobile telecommunications is ableto span a wide variety of deployment scenarios (e.g., Rural, UrbanMacro, Dense Urban, Indoor, etc.) in a flexible and scalable manner. Inparticular, massive MIMO reciprocity-based TDD air interfaces allow forsymbol-level switching and potential configurability that in turn allowfor features to support three primary aspects of 5G air interfaces,namely enhanced Mobile BroadBand (eMBB), massive Machine TypeCommunications (mMTC) and Ultra-Reliable and Low Latency Communications(URLLC).

The disclosed embodiments can also be used with techniques and relatedembodiments described in U.S. patent application Ser. No. 15/940,103,filed Mar. 29, 2018, and U.S. patent application Ser. No. 15/855,148,filed Dec. 27, 2017, each of which is hereby incorporated by referencein its entirety.

FIG. 6 is a diagram of an example embodiment 600 for electroniccomponents that can be used to implement a base station and/or userequipment (UE) including the functions and operational featuresdescribed for the disclosed embodiments. For the example embodiment 600shown in FIG. 6, one or more processors 608 communicate with othercomponents through system bus interconnect 602. For example, the one ormore processors 608 communicate with input/output (I/O) circuitry 604and transmit/receive (TX/RX) circuitry 606 through the system businterconnect 602. Additional circuitry can also be included such aspower supply circuitry and/or other desired circuitry. The TX/RXcircuitry 606 provides one or more cellular radios and are preferablycoupled to a plurality of antennas through which the TX/RX circuitrytransmits and receives RF (radio frequency) signals (e.g., from a fewkHz to 10 GHz and above). The I/O circuitry 604 provides one or moreinterfaces for users, such as graphical user interfaces, and/orconnections to peripheral devices (e.g., displays, keyboards, mice,point device, and/or other I/O peripheral devices). The memory 610 isalso coupled to the system bus interconnect 602 and can be used by theone or more processors 608 to load and/or store instructions, data,and/or other information during operation. One or more data storagedevice(s) 612 are also connected to the system bus interconnect 602 andcan store software or program instructions and/or other desired data orinformation for the operation of the processing system. For example,computer-readable instructions stored in the data storage devices 612can be loaded within the memory 610 and then executed by theprocessor(s) 608 to carry out the functions described herein.

It is noted that different and/or additional components from thosedepicted in FIG. 6 could also be used to implement one or more radiosystems for the embodiments described herein while still takingadvantage of the techniques described herein. It is further noted thatthe system bus interconnect 602 can be implemented as multipleinterconnection buses with our without additional intervening circuitrysuch as routing or switching circuitry. Further, the processor(s) 608can be implemented using one or more programmable integrated circuitsincluding controllers, microcontrollers, microprocessors, hardwareaccelerators, configurable logic devices (e.g., field programmable gatearrays), and/or other programmable integrated circuits that areprogrammed to carry out the function described herein. Further, the oneor more processor(s) 608 can execute instructions stored in anon-transitory tangible computer-readable medium to perform thefunctions described herein. In addition, data storage device(s) 612 canbe implemented as any desired non-transitory tangible medium that storesdata, such as data storage devices, FLASH memory, random access memory,read only memory, programmable memory devices, reprogrammable storagedevices, hard drives, floppy disks, DVDs, CD-ROMs, and/or any othernon-transitory data storage mediums. The memory 610 can be any datastorage medium configured to maintain data storage when powered. Othervariations could also be implemented.

Terms

The following is a glossary of terms used in the present application:

A spatial stream is a sequence of symbols transmitted from an antennaport. The term spatial stream is used in the present disclosure in thecontext of spatial multiplexing. Spatial multiplexing is a transmissiontechnique used in a MIMO (multiple input multiple output) wirelesscommunication system in which multiple spatial streams are transmittedfrom the multiple transmit antenna ports of the MIMO system.

An antenna port is defined such that the physical channel over which asymbol on the antenna port is conveyed can be inferred from the physicalchannel over which another symbol on the same antenna port is conveyed.For example, an antenna port may convey a DMRS over a channel, and theantenna port may convey on the channel a corresponding spatial streamwhose symbols are demodulated using the channel estimate obtained fromthe received DMRS. For another example, an antenna port may convey aPTRS over a channel, and the antenna port may convey on the channel acorresponding spatial stream whose symbols having phase noise trackedand compensated using the PTRS.

A symbol is a complex-valued signal transmitted over aspace-time-frequency resource. Examples of OFDM symbols are DMRS, SRS(Sounding Reference Signal), data channel symbols and control channelsymbols.

A physical channel is an uplink or downlink physical channel. A physicalchannel corresponds to a set of resource elements carrying informationoriginating from the higher layers of a communication protocol stack.Examples of channels are PDSCH (physical downlink shared channel), PUSCH(physical uplink shared channel), PDCCH (physical downlink controlchannel), PUCCH (physical uplink control channel), and PBCH (physicalbroadcast channel).

A resource element is an element in an OFDM resource grid for an antennaport and subcarrier spacing configuration.

CPE (common phase error) is a common phase rotation across all of thesubcarriers for an OFDM transmission.

Phase noise is partial random phase variation over time in a signal.Typically, phase noise is introduced by non-ideal sinusoidal signalsgenerated by oscillators.

A DMRS is a demodulation reference signal which is used for channelestimation purposes in order to allow demodulation of one or morephysical channels, e.g., PDSCH, PUSCH PDCCH, PUCCH, PBCH.

A DMRS port is an antenna port over which a DMRS is transmitted and canbe used to receive the data symbols transmitted on the same antennaport.

A PTRS is a phase tracking reference signal which is used to track andcompensate for the impact of phase noise. A PTRS is also referred toherein as a PNRS (phase noise reference signal). The describedembodiments advantageously facilitate a reduction in the number of DMRSports (and their corresponding spatial streams) upon which PTRS need betransmitted when CPE correlation between one or more spatial streams isdetected. This is particularly advantageous because PTRS generally needto be transmitted densely in time. Generally speaking, relative to DMRS,for example, PTRS need to be transmitted relatively densely in timebecause phase noise tends to vary more frequently over time than thechannel estimate obtained from the DMRS. Thus, for example, it may besufficient for one DMRS to be sent per slot/TTI; whereas, typicallymultiple PTRS need to be sent per slot/TTI, often within each symbolthereof.

A PTRS port is an antenna port over which a PTRS is transmitted.

A CSI-RS is a channel state information reference signal which is usedto calculate the channel state information.

A CSI-RS port is an antenna port over which a CSI-RS is transmitted.

One objective for the 5G air interfaces is to operate from below 1 GHzto 100 GHz carrier frequencies over a large variety of deploymentscenarios in a single technical framework, for example, using OFDM(orthogonal frequency division multiplexing) modulation. For thisobjective, phase noise (PN) becomes a major impairment at carrierfrequencies above 6 GHz. Phase noise introduces two kinds of impairmenton OFDM-based systems: (1) common phase error (CPE) and (2)inter-carrier interference (ICI). CPE is a common phase rotation acrossall of the subcarriers for an OFDM transmission, and CPE manifests as acommon rotation of the demodulated constellation. The phase noise ateach subcarrier frequency also introduces ICI to the neighboringsubcarriers, and this spectral leakage degrades the orthogonality of theOFDM waveform. This degradation is manifested as a “fuzziness” in eachdemodulated constellation point, and the level of ICI can be measured bythe degradation of the EVM (Error Vector Magnitude) of the communicationlink. Phase noise typically increases with the carrier frequency, forexample, one general assumption is that PSD (power spectrum density)associated with phase noise increases by about 20 dB per decade offrequency.

CPE can be estimated in a straightforward manner with a least squaresestimator according to the equation shown below.

${{\hat{J}}_{0}(m)} = {\frac{\sum\limits_{k \in S_{p}}^{\;}{{R_{k}(m)}{X_{k}^{*}(m)}{H_{k}^{*}(m)}}}{\sum\limits_{k \in S_{p}}^{\;}{{{X_{k}^{*}(m)}{H_{k}^{*}(m)}}}}.}$

-   -   For this equation, R_(k) is the received subcarrier values;        X_(k), where k∈S_(p), is the transmitted pilot symbol that is        known at the receiver; H_(k) is the channel estimate; and S_(p)        is the subset of the subcarriers occupied by the pilot. The CPE        for each OFDM symbol within an OFDM transmission is the DC        component of the DFT (discrete Fourier transform) of the        baseband PN (Phase Noise) samples over that symbol duration.

As CPE is constant for all subcarriers within an OFDM symbol and can beestimated, CPE compensation can be performed with the introduction ofPhase Noise Reference Signals (PNRS), also called Phase TrackingReference Signals (PTRS), or other pilots within the OFDM transmissions.The addition of the PNRS/PTRS, therefore, allows for CPE compensationbut only at the expense of additional pilot signal overhead within theOFDM symbols. This CPE estimation based on a static pilot pattern,therefore, has the drawback of high overhead due to required pilotsignaling for the purely pilot aided PN compensation. Moreover,different devices and deployment scenarios have different levels ofrequirement for the PN (phase noise) mitigation. For example, UEs (userequipment) and base stations have significantly different phase noisePSD requirements, and UEs can be categorized into different groups withrespect to PN performance based on their frequency band of operation andwireless system application, such as eMBB (enhanced Mobile BroadBand),URLLC (ultra-reliable low latency communications), mMTC (massive machinetype communications), and/or other use cases.

It is noted that the terminology Phase Noise Reference Signal (PNRS) isused herein interchangeably with Phase Tracking Reference Signal (PTRS)to refer to the same signal. In addition to OFDM waveforms, PNRS/PTRScan also be inserted in SC (Single Carrier) waveforms in astraightforward manner to estimate and compensate the complete PN (PhaseNoise) over that SC waveform. Examples of such single carrier waveformsinclude Single Carrier Frequency Division Multiple Access (SC-FDMA), DFTspread OFDM (DFT-s-OFDM), Null Cyclic Prefix Single Carrier (NCP-SC),etc.

PTRS (phase tracking-reference signal) ports and related signals can beused by base stations(s) to allow the UEs to derive a scalar estimationof the common phase error (CPE) due to the phase noise process which isassumed to be constant over all of the subcarriers of a given symbol ofthe allocated UE bandwidth. This estimate becomes more accurate withincreasing the number of REs (resource elements) allocated to PTRSwithin the scheduled bandwidth of the given UE. In addition, whenmultiple antenna ports are used to transmit from the base station(s) tothe UE, there can be one-to-one mapping or many-to-one mapping from theDMRS (demodulation reference signal) ports to the PTRS ports. The DMRSports are used by the base station(s) to provide signals that facilitatedemodulation operations within the UEs. While the use of PTRS ports andrelated communications can help improve CPE compensation, they can alsolead to inefficiencies with respect to the use of available bandwidthand difficulties arise in the selection and allocation of the PTRS portsby the base station(s).

The disclosed embodiments provide techniques for UEs (user equipment) tomeasure CPE (common phase error) correlations among different receive(or transmit) spatial streams and then to provide feedback to basestation(s) (e.g., gNB) with respect to these cross correlations. For oneexample embodiment, the feedback includes the results of the crosscorrelations such as a correlation matrix or a condensed/transformedversion of it. For one other example embodiment, the feedback includes aselection by the UE of recommended PTRS ports to be associated with itsDMRS ports, and this recommended port list is transmitted back to thebase station(s). The base station(s) (e.g., gNB) then use this crosscorrelation feedback to select and configure the PTRS ports used for oneor more UEs. Other variations can also be implemented while still takingadvantage of the techniques described herein. The described techniquesfor selecting PTRS ports may improve the operation of wirelesstelecommunication systems by enabling them to improve CPE compensationand to more efficiently use available bandwidth.

Example Communication Environments for the Disclosed Embodiments

With respect to the descriptions provided herein, the followingabbreviations are used:

PTRS: Phase Tracking Reference Signal

DMRS: Demodulation Reference Signal

TRP: Transmission Reception Point

gNB: g NodeB (base station)

PSD: Power Spectral Density

PN: Phase Noise

TTI: Transmission Time Interval, the minimum scheduling interval for aUE

Example Architectures of Base Station (BS) and User Equipment (UE)

The following are example architectures that can be used for basestation (BS) and user equipment (UE) implementations within a wirelesscommunication system. As these are example embodiments, it is understoodthat additional and/or different architectures could be used.

At the TRP the following are example architectures:

-   -   One antenna panel only        -   One LO (local oscillator) shared between all antennas of the            panel        -   Multiple LOs shared between the antennas of the panel            -   With common clock    -   Multiple antenna panels        -   One LO shared between all antenna panels        -   One LO per antenna panel            -   With common clock shared between all LOs            -   Separate clock for each/some of the LOs        -   Multiple LOs per panel            -   Common clock per panel            -   One clock for all the LOs in that antenna panel

With Multiple TRP joint transmission of some category (Non CoherentJoint Transmission (NCJT), Dynamic Point Selection (DPS), CoordinatedMulti-Point (CoMP), etc.), there are multiple TRPs and/or multiple gNBsthat can communicate to an UE in a coordinated manner. In such cases,the example architecture can have;

-   -   Separate LO(s) per TRP, different clock(s) per TRP    -   Each of the sub options per TRP as given in previous list

At the UE the following are example architectures:

-   -   One antenna panel only        -   One LO (local oscillator) shared between all antennas of the            panel    -   Multiple antenna panels        -   One LO shared between all antenna panels        -   One LO per antenna panel            -   With common clock shared between all LOs            -   Separate clock for each/some of the LOs

In addition to antennas and panels, there are digital transceiverchains, which are mapped to the antennas/panels using an antenna mappingmatrix. Additional and/or different circuitry and components can also beincluded while still taking advantage of the techniques disclosedherein.

FIGS. 7-9 provide example embodiments for different implementationswhere clock signals and related circuitry are used as LOs for RFchannels within downlink (DL) and/or uplink (UL) circuitry for basestations or UEs. It is noted that the LO signals can be used, forexample, to mix RF signals up to higher frequencies and/or to mix RFsignals down to lower frequencies within the DL and/or UL circuitry forbase stations or UEs.

FIG. 7 is a block diagram of an example embodiment where the same clock,which can be generated by oscillator (OSC) 206, and the same PLL (phaselock loop) 204, which can be a divide-by-N based PLL (xN), are used as asingle LO to generate LO signals that are provided to multiple differentRF channels (RF₁ . . . RF_(X)) 202.

FIG. 8 is a block diagram of an example embodiment where the same clock,which can be generated by oscillator (OSC) 206, is used as an input tomultiple different PLLs (PLL₁ . . . PLL_(Z)) 204, which can each be adivide-by-N based PLL (xN). These different PLLs 204 in combination withthe clock are used as different LOs to generate multiple LO signals thatare provided to multiple sets of different RF channels (RF₁ . . .RF_(X), RF₁ . . . RF_(Y)) 202.

FIG. 9 is a block diagram of an example embodiment where multipleclocks, which can be generated by multiple oscillators (OSC₁ . . .OSC_(Z)) 206, are used as inputs to multiple different PLLs (PLL₁ . . .PLL_(Z)) 204, which can each be a divide-by-N based PLL (xN). Thesedifferent PLLs 204 in combination with the different clocks are used asdifferent LOs to generate multiple LO signals that are provided tomultiple sets of different RF channels (RF₁ . . . RF_(X), RF₁ . . .RF_(Y)) 202.

As explained in further detail below, depending on the architectureimplemented for the base stations and/or UEs, the Phase Noise (PN)characteristics are different. Further, the downlink (DL) parts and theuplink (UL) parts of the implementations can also have different PNcharacteristics and should therefore be considered separately.

Example of Different Varieties of MIMO Transmissions

A base station (BS) for a MIMO communication system will set up multiplespatial streams. The following are examples of communication systemswith such multiple spatial streams:

-   -   SU-MIMO (Single User-MIMO)        -   Single TRP        -   Multi TRP    -   MU-MIMO (Multi-User MIMO)        -   Single TRP        -   Multi TRP    -   For each of these spatial stream examples, the UE communicating        with the base station can be implemented as a SISO (single        input, single output) device or as a MIMO device.

Also for MIMO systems, there is a mapping between the spatial streamsand the transceiver architectures. To simplify the discussions below,the following assumptions are applied, although it is understood thatthe techniques described herein can be applied to other combinations instraight forward manner.

-   -   SS stands for Spatial Stream; TRX stands for Transceiver chain    -   Mapping of SS to Antennas        -   One SS is mapped within one antenna panel (e.g., the SS is            not shared between the antennas on two or more panels)        -   OR One SS is mapped to multiple antenna panels        -   More than one SS can be mapped to one antenna panel    -   One SS transmission involves only one LO        -   Within a TRP, the SS are mapped to TRX such that each SS has            only one LO    -   Multiple SS can share an LO

While the current NR definition supports up to 12 SS, there arediscussions to extend it to 16 SS (e.g., by supporting 16 orthogonalDMRS ports). The techniques described herein can be scaled up to 16 SSbut are not limited to 16 SS. The disclosed techniques can be used forsystems with more than 16 SS as well.

Characteristics of Phase Noise

To describe the phase noise in the system:

-   -   Total phase noise PSD is the combination of the PSD at TX and        PSD at RX.    -   Usually UE will have a lot worse PSD than TRP due to the        relative difference in quality of RF chains at UE and TRP.    -   The UEs in the network will be categorized into UE categories        depending on this RF quality and other transmission capabilities        of that UE. That UE category and/or UE capability and/or UE        feature is expected to reflect the PSD quality to some level.

In an OFDM system, the Phase Noise impact is measured on a per symbollevel via:

-   -   CPE (Common Phase Error)    -   ICI (Inter Carrier Interference)

The PSD of Phase Noise is a combination of:

-   -   PSD of PN of Clock    -   PSD of PN of PLL Loop Filter    -   PSD outside the Loop Filter BW

Now, to compensate the PN for OFDM at less than 40 GHz, estimating andcompensating for CPE is sufficient. CPE is different for each symbol,and is a random variable in time, following a type of random walkprocess. The 40 GHz upper bound is an example of current RF technology;however, it should be understood that the upper bound will likely shiftin the future as RF technology progresses.

Measurement of the Phase Noise Between Spatial Streams

Descriptors of Phase Noise Correlation

Depending on the clocks and LOs involved and their mapping to theantenna elements, the Phase Noise process of different SS can becorrelated to different degrees. As such, the following arecharacterized:

-   -   Dependence of the complete phase noise between SS    -   Dependence of the CPE between SS

With respect to dependence of the phase noise between SS, it isdesirable to estimate exact PN samples over time/SC (subcarrier) per SSand then find the cross correlation between the SS of this complete PNprocess. These will include the impact of CPE and ICI.

With respect to dependence of the CPE between SS, there are a number ofoptions to characterize it as provided below. First, CPE is found for asymbol for each SS. Then, the following options can be performed:

-   -   Compare the instantaneous CPE per SS in that symbol:        -   If all SS are completely correlated, then this CPE should be            the same.        -   If there is partial correlation among some SS, but not the            others, then the CPE of those SS should be similar while            that of the uncorrelated SS will be different.    -   Compare the time series of instantaneous CPE per SS over        multiple symbols in the TTI:        -   There are multiple ways to find the CPE in a symbol per SS.        -   If the CPE is estimated over N symbols out of M in the TTI,            then the time series of CPE is obtained per SS.        -   The cross correlation of the CPE over all or some of the SS            can then be calculated.    -   Compare over multiple TTIs:        -   Knowledge from past TTIs in which the UE has been scheduled            can be used to get more sample points for estimating the            CPE.

Methods to Estimate the CPE

It is proposed to use a toolkit of methods to estimate the CPE dependingon the symbol number and structure. They are introduced here with moredetails being provided below.

-   -   DMRS (demodulation-reference signal) based        -   Use the DMRS which is either front loaded or also can be in            middle of the slot    -   PTRS based        -   Use the PTRS in the PDSCH (physical downlink shared channel)    -   CSI-RS (channel state information-reference signal) based        -   The CSI-RS can be used, present again in PDSCH    -   Blind data based        -   The blind data based methods can be used in symbols.

Depending on the numerology and frame structure, each symbol in the TTIcan support all or some of the above methods. Using all or some of themethods listed above, one can estimate the CPE time series in a TTI.Then, using one of the CPE cross correlation methods listed above, onecan estimate to what degree the phase noise between the SS iscorrelated.

FIG. 10 provides an example diagram of two subframes 500 transmittedfrom a MIMO base station that include two orthogonal PTRS ports 502 withthe PDSCH 508. The PDCCH (physical downlink control channel) 504 symbolsare included at the beginning of each frame followed by DMRS(demodulation reference signal) symbols 506 for 12 spatial streams.

Feedback of the Correlation of PN Between SS

The following methods are proposed to feedback the correlation from theUE to the base station. The base station can then use this feedback toallocate PTRS ports to UEs.

Feedback Method Type 1:

Send back the raw or quantized version of the cross correlation matrix.The matrix looks like the matrix below:

SS_xcorr = [C_1_1, C_1_2, …  , C_1_N; C_2_1, C_2_2, C_2_3, …  , C_2_N; …  ; …  ; C_N_1, C_N_2, …  , C_N_N]${SS}_{xcorr} = \begin{bmatrix}C_{11} & \ldots & C_{1N} \\\vdots & \ddots & \vdots \\C_{N\; 1} & \; & C_{NN}\end{bmatrix}$

It is noted that not all values may typically be estimated by a specificUE. It depends on the number of DMRS that a UE can receive. The UE canbe configured to send feedback for cross correlation back to the gNBover a UCI (Uplink scheduling Control Information) message, a MAC CE(Media Access Control-Control Element), a RRC (Radio Resource Control)message, and/or some other desired message channel.

Example

If a TRP transmits SS 1,2,3,4,5,6 in one DMRS group (which are usuallyQuasi Co-Located (QCLed)) and 6 other SS in a second DMRS group; and ifUE1 is configured to receive data addressed to it in spatial streams1,2,3,4 out of the 12 SS transmitted by that TRP; and if UE1 can alsoreceive the other DMRS in the group, i.e. corresponding to SS 5 and 6,then the UE1 can use the DMRS to equalize 6 out of the 12 spatialstreams (i.e., SS 1,2,3,4,5,6) even though only 4 contain data addressedto it. And UE 1 can fill in a 6×6 cross correlation matrix.

After this matrix is prepared, it can be signaled back by the UE in anumber of ways.

-   -   Feedback all elements of the matrix: [C_1_1, C_1_2, . . . ,        C_1_N, C_2_1, C_2_2, C_2_3, . . . , C_2_N, . . . , C_N_1, C_N_2,        . . . , C_N];    -   Feedback only the off-diagonal terms of the matrix: [C_1_2,        C_1_3, . . . , C_1_N, C_2_1, C_2_3, . . . , C_2_N, . . . ,        C_N_1, C_N_2, . . . , C_N_N−1];    -   Feedback the averaged cross correlation per pair of Spatial        Streams;        -   combine C_1_2 and C_2_1 into Ceff_1_2=(C_1_2+C_2_1)/2        -   send back [Ceff_1_2, Ceff_1_3, Ceff_1_4, . . . , Ceff_1_N,            Ceff_2_3, Ceff_2_4, . . . , Ceff_2_N, Ceff_3_4, . . . ,            Ceff_3_N, . . . Ceff_N−1_N]    -   Feedback only those cross-correlation values which are        above/below a certain threshold;    -   Feedback only those cross-correlation values which are        above/below a certain SS-specific threshold;    -   Feedback quantized (e.g., linear or logarithmic)        cross-correlation values, for example the cross-correlation        value has to be mapped to a two-digit binary number; and/or    -   Consider all the options mentioned above but feedback only those        values that differ from the previous reporting.    -   It is further noted that additional and/or different feedback        techniques could also be used by the UE to send cross        correlation feedback information back to the TRP, such as a base        station.

Feedback Method Type 2:

In this method, the concept is to send back to the TRP the UE'ssuggestion for allocating the PTRS ports to it. The UE selects theoptimum number of PTRS ports it needs and which DMRS ports with whichthey are associated using the cross correlation matrix it has computed.The raw cross correlation data is not sent back. Instead, the UErecommendation for the PTRS ports it needs is sent back. It is up to thebase station scheduler to take into consideration such feedback from allrelevant scheduled UEs and allocate the actual number of PTRS ports andmap them to the DMRS ports and spatial streams. The feedback can beconfigured to be sent back to the gNB over a UCI message, a MAC CE, aRRC command, and/or some other desired message channel.

Example

Continuing the example from the feedback Type 1 above, the UE measuresthe 6×6 cross correlation matrix, and in this instance finds that thephase noise process on spatial streams 1 and 2 are highly correlated,and that those on spatial streams 3, 4, 5, 6 are highly uncorrelated. Inthat case, it may request the TRP to allocate five spatial streams andto map PTRS port 1 to DMRS port 1, to map no PTRS ports to DMRS port 2,and to map PTRS ports 2 through 5 to DMRS ports 3 through 6,respectively. It is noted that DMRS port 5 and 6 are used for another UEfor this example.

Example Flow Diagrams

FIGS. 11A-C provide an example flow diagram for performing the PNcorrelation at the UEs and for the feedback of these correlations fromthe UE to the base station. It is noted that although the discussionsherein focus on the DL, these methods can be extended to UL in a similarmanner.

Looking first to FIG. 11A, at block 602, when PTRS communications aresupported by the base station, the process starts off with transmittingSlot/TTI with 1 PTRS per DMRS port with some known time frequencydensity. Otherwise, there is lesser PTRS per DMRS ports according tosome implicitly/explicitly indicated association rule. Further:

-   -   There is one DMRS port per spatial stream;    -   The spatial streams can be transmitted from any of the setups        indicated: Multi TRP, One TRP, to single UE, to multiple UEs;        and    -   Time frequency density/location can be implicitly/explicitly        indicated to the UE.

Next, at block 604, at each UE scheduled in that TTI, the following aredone in the front loaded DMRS symbol:

-   -   Estimate CPE per Spatial Stream using all the DMRS in the        scheduled resource blocks for that UE; and    -   DMRS from spatial streams not meant for the given UE group or        DMRS group are also used if possible (this is optional). If not,        limit the CPE estimation to SS meant for that UE group or DMRS        group only

Next, at block 606, at each UE scheduled in that TTI, the following aredone in the symbols that have PTRS (special case is if every PDSCHsymbol has a PTRS):

-   -   Estimate CPE per Spatial Stream using all the PTRS in the        scheduled resource blocks for that UE; and    -   PTRS from spatial streams not meant for the given UE are also        used if possible (this is optional). If not, limit the CPE        estimation to use PTRS in SS meant for that UE only.

Next, at block 608, at each UE scheduled in that TTI, if additional(non-front loaded) DMRS symbol present, the following are done:

-   -   Estimate CPE per Spatial Stream using all the DMRS in the        scheduled resource blocks for that UE; and    -   DMRS from spatial streams not meant for the given UE group or        DMRS group are also used if possible (this is optional). If not,        limit the CPE estimates to SS meant for that UE group or DMRS        group only

Next, at block 609, if some of the symbols in the TTI contain a CSI-RStransmission, the UE can use the CSI-RS to derive the CPE if sufficientnumber of CSI-RS are available to achieve reliable CPE estimation.

Next, at block 611, at each UE scheduled in that TTI, if a selectedPDSCH symbol has no DMRS or PTRS or CSI-RS, then estimate the CPE withblind method. This is done only in SS meant for that UE.

Next, at block 612, the cross correlation of the CPE is calculatedacross the spatial streams. This is done for as many SS as possible.

If the Type 1 Feedback method is being used, at block 614, the UE thentransmits the complete N×N Cross Correlation matrix, or one of thecondensed and transformed version of it, back to the base station.

If the Type 2 Feedback method is being used, at block 616, the UE thenselects the optimum number of PTRS ports it needs and which DMRS portswith which they are associated. This recommended PTRS port list istransmitted back to the base station(s) by the UE.

Finally, at block 618, the base stations (e.g., gNB) updates PTRSallocation and mapping to DMRS ports based on reports received from UEs.

Extension/Modification for Multi TTI Operation

The following provides an extension of the example flow provided inFIGS. 11A-C for OFDM to multiple TTIs. The proposed method uses the CPEestimates from the last M number of TTIs for which a specific UE wasscheduled with a similar transmission mode setup.

The proposed method for each TTI-i is as follows:

-   -   If the UE is scheduled with Transmission scheme setup Y:        -   Estimate CPE in each possible symbol of the TTI as provided            in the example of FIGS. 11A-C; and        -   Obtain Time Series of CPE per symbol per spatial stream.    -   If previous TTI(s) that used same Transmission scheme Y were        present:        -   Concatenate the CPE Estimates of Current TTI-i with the past            TTI(s) and update the Cross Correlation Matrix (SS_xcorr);            -   OR        -   Find SS_xcorr per individual TTI and combine them with            either averaging or a variety of exponentially weighted            averaging to get a new update of SS_xcorr.    -   Send back the updated SS_xcorr or the recommended PTRS port        configuration settings back to the gNB depending on the Feedback        Method Type 1 or 2 used.    -   Wait for next TTI when the UE is scheduled.

Extension/Modification for Single Carrier Modulations

For the case of single carrier waveforms [SC=Single Carrier TransmissionScheme], such as Null CP Single Carrier Waveform, or SC-FDMA or any ofthe other candidates in the single carrier family, the problem of phasenoise estimation and compensation still exists. However, the OFDM typeCommon Phase Error (CPE) is not relevant as the phase noise does notneed to be compensated in frequency (per subcarrier) and instead needsto be compensated in time.

Some techniques for such PN time compensation are:

-   -   Time domain Pilot aided compensation;    -   Time domain Cyclic Prefix aided compensation; and    -   Time domain blind compensation.

In addition, the proposed techniques described herein can be extended tosuch single carrier scenario. For example, consider a MU-MIMO type SCsystem where multiple UEs are scheduled on the same time frequencyresource. Each UE gets a UE specific pilot that is pre-coded in the samemanner as the data to the UE. This is called the SC DMRS pilot. Thereare additional SC PTRS pilots that can be used in the system. Each SCPTRS is associated to one or more SC DMRS port and share the sameprecoding as exactly one SC DMRS port. The algorithm can then beimplemented the same as in FIGS. 11A-C above for the OFDM case but PTRSis replaced by SC PTRS and DMRS is replaced by SC DMRS.

As noted above, although the discussions herein focus on the DL, thesemethods can be extended to UL in a similar manner.

It is noted that the disclosed embodiments can be used with respect to avariety of OFDM-based transmission schemes for RF communication systems.It is also noted that as used herein, a “radio frequency” or RFcommunications means an electrical and/or electro-magnetic signalconveying useful information and having a frequency from about 3kilohertz (kHz) to thousands of gigahertz (GHz) regardless of the mediumthrough which such signal is conveyed. The OFDM-based transmissions maybe transmitted through a variety of mediums (e.g., air, free space,coaxial cable, optical fibers, copper wire, metal layers, and/or otherRF transmission mediums). As one example, the disclosed embodimentscould be used for millimeter (mm) wave transmissions between 30-300 GHzhaving wavelengths of 1-10 mm (e.g., a transmission range of 71-76 GHz)if OFDM-based modulation were used for the mm wave transmissions. Inaddition, the disclosed embodiments will likely be useful for 5Gsolutions up to 40 GHz where OFDM-based modulations are more likely tobe implemented. For example, 5G frequency ranges and bands around 28GHz, 39 GHz, and/or other frequency ranges or bands where OFDM-basedmodulation is used for RF transmissions will benefit from the disclosedtechniques. It is further noted that example wireless communicationsystems within which the disclosed techniques can be applied are alsodescribed in U.S. Published Patent Application No. 2015-0303936 (Ser.No. 14/257,944) and U.S. Published Patent Application No. 2015-0305029(Ser. No. 14/691,339), each of which is hereby incorporated by referencein its entirety.

FIG. 12 is a block diagram of an example embodiment for circuitry thatcan be used to provide a baseband receiver, a baseband transmitter,multi-FPGA processing circuitry, and a real-time processor with respectto the embodiment of FIG. 5. The embodiment of FIG. 12 provides tworeceive/transmit streams and related processing circuitry.

Looking to the embodiment of FIG. 12, two analog-to-digital converters(ADC1 802-1, ADC2 802-2) receive analog baseband signals and outputsampled digital baseband signals 804 (i.e., sampled time-domain basebandreceive signals) to two demodulators/equalizers 806. Thedemodulators/equalizers (DEMODULATOR/EQUALIZER 1 806-1,DEMODULATOR/EQUALIZER 2 806-2) demodulate and equalize the respectivereceive signals. Due to the complexity of the MIMO (multiple inputmultiple output) equalization task, some parts of the relatedfunctionality are realized by a separate MIMO processing circuitry (MIMOPROCESSING 808). Specifically, this MIMO processing circuitry 808performs the MIMO channel estimation and the calculation of theequalizer weights 812. For this, it uses the (pre-processed) pilotsignals/symbols 814 extracted from both received baseband signals asinput. These (pre-processed) pilot signals 814 are provided by thedemodulators/equalizers 806. The equalizer weights 812 (W1, W2)calculated by the MIMO processing circuitry 808 are fed back to thedemodulators/equalizers 806, which can perform the final MIMOequalization using these equalizer weights 812. To support this finalMIMO equalization task, the demodulators/equalizers 806 can exchangeintermediate equalization results. The final output of thedemodulators/equalizers 806 are equalized QAM (quadrature amplitudemodulation) symbols 816 for both receive streams. These equalized QAMsymbols 816 are provided to the MIMO processing circuitry 808, which candistribute the equalized QAM symbols 824 to multiple decoders (DECODER822). It is noted that the upper set of decoders 822 can be used fordecoding the first receive stream and the lower set of decoders 822 canbe used for decoding the second stream. The decoders 822 output decodeddigital receive data 828 plus CRC (cyclic redundancy check) results pertransport block to the MAC support FPGA 826. The MAC support FPGA 826can collect the output data 828 of all decoders 822, can further processthem, and can provide them to the real-time processor (REAL-TIMEPROCESSOR 832) in a synchronized and consistent manner. The real-timeprocessor 832 can perform further operations on the received data 828(and CRC results) provided by the MAC support FPGA 826. Further, it canprovide receiver (RX) control information 836 to the MAC support FPGA826 and/or other receiver FPGAs (not shown) to control and configure therespective receivers. For example, the real-time controller 832 canprovide the control data 836 for all decoders 822 per subframe to theMAC support FPGA 826, and the MAC support FPGA 826 can distribute thesecontrol data 838 to each decoder 822 to provide the configuration usedto decode the related transport block. A similar functionality can beprovided by the real-time processor 832 for the transmit paths. Uncodeddigital transmit data 842 and related transmitter (TX) control data 844are sent from the real-time processor 832 to the MAC support FPGA 826,which distributes the digital transmit data 846 as well as therespective encoder/modulator control data 848 to the twomodulators/encoders (MODULATOR/ENCODER 1 852-1, MODULATOR/ENCODER 2852-2). The modulators/encoders 852 encode the transmit data 846 andperform the transmit modulation, e.g., generate the digital time-domainbaseband transmit signals 854. These digital time-domain basebandtransmit signals 854 are sent by the modulators/encoders 852 to thedigital-to-analog converters (DAC1 856-1, DAC2 856-2). The DACs 856receive the digital baseband signals 854 and output analog basebandsignals. It is noted that demodulators/equalizers, modulators/encoders,MIMO processing circuitry, and decoders can be implemented usingmultiple parallel FPGAs.

The disclosed embodiments can also be used for OFDM-based transmissionschemes for massive MIMO cellular telecommunication systems as describedin U.S. Published Patent Application 2015/0326291, entitled “SIGNALINGAND FRAME STRUCTURE FOR MASSIVE MIMO CELLULAR TELECOMMUNICATIONSYSTEMS,” which is hereby incorporated by reference in its entirety.Such massive MIMO (multiple input, multiple output) communicationsystems can be used for 5G dynamic TDD (time division duplex) airinterfaces. The 5G (5^(th) generation) mobile telecommunications is ableto span a wide variety of deployment scenarios (e.g., Rural, UrbanMacro, Dense Urban, Indoor, etc.) in a flexible and scalable manner. Inparticular, massive MIMO reciprocity-based TDD air interfaces allow forsymbol-level switching and potential configurability that in turn allowfor features to support three primary aspects of 5G air interfaces,namely enhanced Mobile BroadBand (eMBB), massive Machine TypeCommunications (mMTC) and Ultra-Reliable and Low Latency Communications(URLLC).

The disclosed embodiments can also be used with CPE compensationtechniques and related embodiments described in FIGS. 13 through 14 andin U.S. patent application Ser. No. 15/855,148, filed Dec. 27, 2017,which claims priority to U.S. Provisional Patent Application Ser. No.62/443,226, entitled “BLIND COMMON PHASE ERROR (CPE) COMPENSATION FOROFDM SYMBOLS IN WIRELESS COMMUNICATION SYSTEMS,” each of which is herebyincorporated by reference in its entirety.

Looking now to FIG. 13, a block diagram is provided of an exampleembodiment 200 for symbol processing for OFDM transmissions. Atime-frequency synchronization processor 202 receives incoming symbols201 from OFDM transmissions and aligns the start of each OFDM symbol 201for the FFT (fast Fourier transform) operations. The FFT OFDMdemodulator 204 receives the output of the time-frequencysynchronization processor 202 and demodulates the OFDM symbol to extractsubcarriers using an FFT operation. The channel estimator 208 receivesthe subcarriers and uses pilot information within the subcarriers togenerate an estimate of the channel response. The equalization processor206 receives the channel estimate from the channel estimator 208 andapplies it to the extracted subcarriers from the OFDM demodulator 204 togenerate equalized OFDM subcarriers. The CPE estimator 212 receives theequalized OFDM subcarriers and applies one or more blind algorithms 214(e.g., pilot-aided blind method, blind-only method) to generate a CPEestimate, although pilot only estimation can also be applied. The CPEcompensation processor 210 then receives the CPE estimate from the CPEestimator 212 and applies it to the equalized OFDM subcarriers tocompensate for the CPE. The compensated OFDM subcarriers are thendemodulated by the demodulator 216 to generate demodulated data 209. Forexample, this demodulation can produce a decision regarding whichconstellation point was transmitted within a modulation scheme (e.g., 16QAM) applied to the transmitted symbols for processing.

FIG. 14 is a block diagram of an example embodiment 300 where the CPEestimator 212 includes multiple estimation algorithms including a pilotonly CPE estimation algorithm 304, a blind only CPE estimation algorithm214A, and a pilot aided blind CPE estimation algorithm 214B. The CPEestimator 212 receives a control signal 302 that determines which CPEestimation algorithm is applied to any particular OFDM symbol. Thiscontrol signal 302, for example, can be generated by one or more controlprocessors. For the embodiment, the CPE compensator 210 includes adigital mixer 306 that mixes the CPE estimate 308 from the CPE estimator212 with a compensated, or de-rotated, version 315 of the equalized OFDMsubcarriers 312 to generate the CPE compensated OFDM subcarriers 314.The CPE estimate 308 is provided to an accumulator 317 that accumulatesthe CPE estimate 308 with the output 313 of a selector 307 to produce anaccumulated CPE estimate 303, which is provided to a delay block 319that delays the accumulated CPE estimate 303 by one OFDM symbol. Thus,the delay block 319 produces an accumulated CPE estimate 309 associatedwith the previous OFDM symbol, whereas the accumulator 317 produces anaccumulated CPE estimate 303 associated with the current OFDM symbol.The delayed accumulated CPE estimate 309 is provided to an input of theselector 307 and a zero value is provided to the other input of theselector 307. The control signal 302 controls the selector 307 to selectthe delayed CPE estimate 309 when the current OFDM symbol is absentpilot symbols for estimating CPE and selects the zero input when pilotsymbols for estimating CPE are present, or embedded, in the current OFDMsymbol, as well as when the system is at rest and in response to thereceiver transitioning to the blind-only method 214A from the pilot-onlymethod 304 or pilot-aided method 214B. The delayed accumulated CPEestimate 309 is also provided to a second mixer 311 that mixes theequalized subcarriers 312 of the current OFDM symbol to generate thecompensated version 315 of the equalized OFDM subcarriers 312. Thecompensated version 315 of the equalized OFDM subcarriers 312 are alsoprovided to the CPE estimator 212, which uses them to compute the CPEestimate 308. Preferably, the digital mixer 306 forms a unitaryamplitude complex value having a phase, or offset angle, that is anegated version of the CPE estimate 308 and multiplies the compensatedversion of the equalized OFDM subcarriers 315 by the formed complexvalue to generate the CPE compensated OFDM subcarriers 314. Similarly,the second mixer 311 forms a unitary amplitude complex value having aphase, or offset angle, that is a negated version of the delayedaccumulated CPE estimate 309 and multiplies the equalized OFDMsubcarriers 312 by the formed complex value to generate the compensatedversion 315 of the equalized OFDM subcarriers 312. As described above,the CPE estimator 212 uses the de-rotated/compensated equalizedsubcarriers 315 to generate the CPE estimate 308. For example, in thecase of an N-subcarrier FFT, the CPE estimator 212 uses N subcarriers togenerate the CPE estimate 308, and the mixer 306 applies the CPEestimate 308 to the N subcarriers. It is noted that in the case of anOFDM symbol embedded with pilot symbols that are used to compute the CPEestimate 308, the mixer 311 will not modify the equalized OFDMsubcarriers 312 (i.e., will mix them with a unitary value by operationof the selector 307 to output a zero-valued phase, or angle, that, asthe exponent of the formed complex value, will cause it to be unitary).

It is noted that the methods and related systems are provided that adaptthe density of the PN reference signals or pilots within the OFDMtransmissions in a dynamic and/or semi-static manner based on theperformance of the purely pilot aided CPE compensation method 304, blindCPE compensation method 214A, and/or the pilot aided blind CPEcompensation method 214B. This density of PN reference signals or pilotscan be adapted in time and/or frequency. In addition, a receiving device(e.g., one or more UEs) can send control messages back to a transmittingdevice (e.g., one or more base stations) indicating the performancelevel associated with the CPE compensation methods being employed. Forexample, the number of symbols within a duration including PN referencesignals or pilots can be reduced by the transmitting device as long asthe pilot aided CPE compensation method continues to provide adequateperformance. Once all PN reference signals are removed, the blind CPEcompensation method 214A can be used as long as it continues to provideadequate performance. Other variations could also be implemented whilestill taking advantage of the blind CPE estimation techniques describedherein.

It is noted that the disclosed embodiments can be used with respect to avariety of OFDM-based transmission schemes for RF communication systems.It is also noted that as used herein, a “radio frequency” or RFcommunications means an electrical and/or electro-magnetic signalconveying useful information and having a frequency from about 3kilohertz (kHz) to thousands of gigahertz (GHz) regardless of the mediumthrough which such signal is conveyed. The OFDM-based transmissions maybe transmitted through a variety of mediums (e.g., air, free space,coaxial cable, optical fibers, copper wire, metal layers, and/or otherRF transmission mediums). As one example, the disclosed embodimentscould be used for millimeter (mm) wave transmissions between 30-300 GHzhaving wavelengths of 1-10 mm (e.g., a transmission range of 71-76 GHz)if OFDM-based modulation were used for the mm wave transmissions. Inaddition, the disclosed embodiments will likely be useful for 5Gsolutions up to 40 GHz where OFDM-based modulations are more likely tobe implemented. For example, 5G frequency ranges and bands around 28GHz, 39 GHz, and/or other frequency ranges or bands where OFDM-basedmodulation is used for RF transmissions will benefit from the blind CPEcompensation techniques described herein for the disclosed embodiments.It is further noted that example wireless communication systems withinwhich the disclosed blind CPE compensation techniques can be applied arealso described in U.S. Published Patent Application No. 2015-0303936(Ser. No. 14/257,944) and U.S. Published Patent Application No.2015-0305029 (Ser. No. 14/691,339), each of which is hereby incorporatedby reference in its entirety.

Advantageously, embodiments described may provide reduced overheadand/or latency in the beam management process, particularly inmillimeter wave scenarios. More specifically, the embodiments may reducethe communication overhead between the BS and UE and may shorten thebeam refinement procedure. This may be due to the dual use of thereference signals (e.g., SS) for both synchronization and nested beamlinkage, as well as the BS potentially transmitting fewer narrow beamsduring its beam sweep. Additionally, the linkage between the narrow andwide beams provides the ability for the BS and UE to fallback to usingthe wider beam to communicate when the narrow beam quality isinsufficient. This ability to fallback on the wider beam mayadvantageously increase the robustness of the system. This increasedrobustness may also reduce the need for procedures to recover from beamfailure.

Advantageously, embodiments described may provide improved beamreporting, particularly in millimeter wave scenarios. More specifically,given that a UE may have limited computational capability, embodimentsmay accomplish an improvement in beam selection by more efficientlyusing the UE's limited computational capability to select the bestbeam(s). This may be particularly advantageous in the NR context giventhat relatively wide range of differing UE categories.

Radio Frequency Beam Management

The embodiments of the methods, or procedures, described in the FIGS. 15through 18 may be performed by systems, including user equipment (UE)and base stations (e.g., eNB, gNB), whose hardware and softwarecomponents are described in FIGS. 1 through 14 and which are furtherconfigured to perform the various steps, functions, operations, etc.described in the FIGS. 15 through 18 other portions of the instantdisclosure.

A radio frequency beam pair link in the downlink is a link defined by atransmitting beam at the gNB and a receiving beam at the UE.

A radio frequency beam pair link in the uplink is a link defined by atransmitting beam at the UE and a receiving beam at the gNB.

A beam quality metric is information that indicates the quality of aradio frequency beam transmitted by a radio frequency transmitter andreceived by a radio frequency transmitter. The beam quality metric maybe based on a received signal strength, a received signal quality, or acombination thereof. For example, a beam quality metric may be receivedsignal strength indication (RSSI), reference signal received power(RSRP), synchronization signal received power (SSRP), signal to noiseratio (SNR), signal to interference plus noise ratio (SINR), channelquality information (CQI), rank information (RI), precoder matrixinformation (PMI), or other metrics.

A beam failure is an event where the beam quality of the beam failuredetection reference signal (RS) that is associated with the beamtriggers a pre-configured beam failure triggering condition.

Beam refinement means selecting a narrow beam that is different from thecurrently selected beam where the current beam might be broad or narrow,and the new beam provides improvement in beam quality metric over thecurrent beam.

A beam failure recovery procedure is a procedure that is triggered by abeam failure and works to recover and re-establish a beam pair linkbetween the gNB and the UE.

Beam switching means selecting a new broad or narrow beam that isdifferent from the currently selected beam where the current beam mightbe broad or narrow, and the new beam may or may not provide improvementin beam quality metric over the current beam.

Beam broadening means selecting a broad beam that is different from thecurrently selected narrow beam where the current narrow beam isassociated to the broad beam by virtue of being nested within the broadbeam.

Embodiments are contemplated in which the beam broadening or refiningmay occur at the gNB and/or the UE.

Beam Management Definitions.

Various definitions follow, which are taken primarily from the 3rdGeneration Partnership Project, Technical Specification Group RadioAccess Network, Study on New Radio Access Technology, Physical LayerAspects (Release 14), which may be found at the perma-linkhttp://www.3gpp.org/ftp/Specs/archive/38_series/38.802/38802-e00.zip.

Beam management: a set of L1/L2 (Level 1/Level 2) procedures to acquireand maintain a set of TRP(s) and/or UE beams that can be used for DL andUL transmission/reception, which include at least following aspects:

-   -   Beam determination: TRP(s) or UE to select its own Tx/Rx        beam(s).    -   Beam measurement: TRP(s) or UE to measure characteristics of        received beamformed signals.    -   Beam reporting: UE to report information of beamformed signal(s)        based on beam measurement.    -   Beam sweeping: operation of covering a spatial area, with beams        transmitted and/or received during a time interval in a        predetermined way.

Beam correspondence

-   -   Tx/Rx beam correspondence at the TRP holds if at least one of        the following is satisfied:        -   The TRP is able to determine a TRP Rx beam for the uplink            reception based on the UE's downlink measurement on the            TRP's one or more Tx beams.        -   The TRP is able to determine a TRP Tx beam for the downlink            transmission based on the TRP's uplink measurement on the            TRP's one or more Rx beams.    -   Tx/Rx beam correspondence at the UE holds if at least one of the        following is satisfied:        -   The UE is able to determine a UE Tx beam for the uplink            transmission based on the UE's downlink measurement on the            UE's one or more Rx beams.        -   The UE is able to determine a UE Rx beam for the downlink            reception based on the TRP's indication based on an uplink            measurement on the UE's one or more Tx beams.        -   The Capability indication of UE beam correspondence related            information to the TRP is supported.

L1/L2 Beam Management Procedures

-   -   The following DL L1/L2 beam management procedures are supported        within one or multiple TRPs:        -   P-1: is used to enable UE measurement on different TRP Tx            beams to support selection of TRP Tx beams/UE Rx beam(s).            -   For beamforming at the TRP, it typically includes a                intra/inter-TRP Tx beam sweep from a set of different                beams.            -   For beamforming at the UE, it typically includes a UE Rx                beam sweep from a set of different beams.        -   P-2: is used to enable UE measurement on different TRP Tx            beams to possibly change inter/intra-TRP Tx beam(s).            -   From a possibly smaller set of beams for beam refinement                than in P-1. Note that P-2 can be a special case of P-1.        -   P-3: is used to enable UE measurement on the same TRP Tx            beam to change the UE Rx beam in the case the UE uses            beamforming.

Beam Reporting

-   -   At least network triggered aperiodic beam reporting is supported        under P-1, P-2, and P-3 related operations.    -   UE measurement based on RS for beam management (at least CSI-RS)        is composed of K (=total number of configured beams) beams, and        the UE reports measurement results of N selected Tx beams, where        N is not necessarily a fixed number. Note that the procedure        based on RS for mobility purpose is not precluded.    -   Reporting information at least includes measurement quantities        for N beam (s) and information indicating NDL Tx beam(s), if        N<K. Specifically, when a UE is configured with K′>1 non-zero        power (NZP) CSI-RS resources, a UE can report N′ CRIs (CSI-RS        Resource Indicator).

Higher layer parameters of UE configuration for beam reporting

-   -   N≥1 reporting settings, M≥1 resource settings        -   The links between reporting settings and resource settings            are configured in the agreed CSI measurement setting.        -   CSI-RS based P-1 & P-2 are supported with resource and            reporting settings.        -   P-3 can be supported with or without reporting setting.    -   A reporting setting at least includes:        -   Information indicating selected beam(s)        -   L1 measurement reporting        -   Time-domain behavior: e.g. aperiodic, periodic,            semi-persistent        -   Frequency-granularity if multiple frequency granularities            are supported.    -   A resource setting at least includes:        -   Time-domain behavior: e.g. aperiodic, periodic,            semi-persistent,        -   RS type: NZP CSI-RS at least,        -   At least one CSI-RS resource set, with each CSI-RS resource            set having K≥1 CSI-RS resources.            -   Some parameters of K CSI-RS resources can be the same,                e.g. port number, time-domain behavior, density and                periodicity if any.

Beam Reporting

-   -   Two alternative schemes have been identified for beam reporting:        -   Alt-1: TRP TX beam(s) received by UE RX beam set(s).        -   Alt-2: TRP TX beam(s) received by UE antenna group(s).

Beam Reporting Alt-1

-   -   The UE reports information about TRP Tx Beam(s) that can be        received using selected UE Rx beam set(s).    -   An Rx beam set refers to a set of UE Rx beams that are used for        receiving a DL signal.        -   One example of how to construct the Rx beam set is that each            of Rx beam in a UE Rx beam set corresponds to a selected Rx            beam in each panel.    -   For UEs with more than one UE Rx beam set, the UE can report TRP        Tx Beam(s) and an identifier of the associated UE Rx beam set        per reported TX beam(s).    -   Different TRP Tx beams reported for the same Rx beam set can be        received simultaneously at the UE.    -   Different TRP TX beams reported for a different UE Rx beam set        may not be possible to be received simultaneously at the UE.

Beam Reporting Alt-2

-   -   The UE reports information about TRP Tx Beam(s) per UE antenna        group basis.    -   A UE antenna group refers to a receive UE antenna panel or        subarray.    -   For UEs with more than one UE antenna group, the UE can report        TRP Tx Beam(s) and an identifier of the associated UE antenna        group per reported TX beam.    -   Different TX beams reported for different antenna groups can be        received simultaneously at the UE.    -   Different TX beams reported for the same UE antenna group may        not be possible to be received simultaneously at the UE

Beam Reporting

-   -   NR also supports the following beam reporting considering L        groups where L>=1 and each group refers to a Rx beam set (Alt1)        or a UE antenna group (Alt2) depending on which alternative is        adopted. For each group l, the UE reports at least the following        information:        -   Information indicating the group at least for some cases,        -   Measurement quantities for N₁ beam (s),            -   Support L1 RSRP and CSI report (when CSI-RS is for CSI                acquisition),        -   Information indicating N₁ DL Tx beam(s) when applicable.    -   This group-based beam reporting is configurable per UE basis.        This group based beam reporting can be turned off per UE basis        e.g., when L=1 or N₁=1. Note that no group identifier is        reported when it is turned off.

Definition of Quasi-Colocation (QCL)

-   -   Two antenna ports are said to be quasi co-located if properties        of the channel over which a symbol on one antenna port is        conveyed can be inferred from the channel over which a symbol on        the other antenna port is conveyed. QCL supports the following        functionalities at least:        -   Beam management functionality: at least including spatial            parameters        -   Frequency/timing offset estimation functionality: at least            including Doppler/delay parameters        -   RRM management functionality: at least including average            gain    -   For DM-RS antenna ports, NR supports:        -   All ports are quasi-colocated.        -   Not all ports are quasi-colocated.    -   DMRS ports grouping is supported, and DMRS ports within one        group are QCL-ed, and DMRS ports in different groups are        non-QCL-ed. NR supports with and without a downlink indication        to derive QCL assumption for assisting UE-side beamforming for        downlink control channel reception.    -   For CSI-RS antenna ports,        -   Indication of QCL between the antenna ports of two CSI-RS            resources is supported.            -   By default, no QCL should be assumed between antenna                ports of two CSI-RS resources.            -   Partial QCL parameters (e.g., only spatial QCL parameter                at UE side) should be considered.        -   For downlink, NR supports CSI-RS reception with and without            beam-related indication,            -   When beam-related indication is provided, information                pertaining to UE-side beamforming/receiving procedure                used for CSI-RS-based measurement can be indicated                through QCL to UE            -   QCL information includes spatial parameter(s) for UE                side reception of CSI-RS ports        -   Indication of QCL assumption associated with subset of QCL            parameters between the antenna ports of two RS resources is            supported.        -   By default (i.e., the UE is not indicated), antenna port(s)            transmitted on different control channels cannot be assumed            to be quasi-collocated except for spatial domain QCL            assumptions.

Aspects of a beam management and recovery procedure will now bedescribed. Due to the characteristics of a mobile radio channel, thequality of a beam can vary between very high and very low, and changesmight happen very fast or gradually. As beam failure is an undesirableevent and recovering from such a failure can cause an interruption inthe connection between the gNB and UE, we aim to preempt such a failurewhen possible. When a beam failure occurs in spite of attempts topreempt it, we aim to recover from the failure with minimum latencywithout triggering Radio Link Failure.

FIG. 15 is a diagram illustrating interplay of beam management, beamrecovery and radio link failure. During an idle state, per block 1512 aninitial access procedure includes the P1 procedure where a broadbeam-based link will be setup between the gNB and the UE. Once the UE isin the RRC Connected state, per block 1532 UE Specific CSI-RS areconfigured and beam measurement and reporting settings are alsoconfigured. This is followed, per block 1514, by beam refinement wherethe narrow beam based PDCCH and PDSCH are setup. Per block, the PDCCHcan also be optionally transmitted on broad beams and/or multiple beamsfor robustness. The beam pair link quality is tracked with beammeasurements (block 1532) using a combination of thresholds and timers.This tracking can happen at either the gNB or the UE as explained below.Depending on the tracking algorithm, per block 1516 beam broadening isattempted and if that is unsuccessful, per block 1518 beam failure canbe triggered. Multiple threshold levels can be set to decide whether toattempt beam refinement and broadening or directly trigger beam failure.Additionally, different beam quality metrics may be associated with thedifferent threshold levels. For example, a first beam quality metric maybe associated with a threshold level used to determine whether toperform beam switching/broadening (e.g., a channel quality beam qualitymetric, e.g., CQI or PMI or RI), whereas a second beam quality metricmay be associated with a threshold level used for beam failure detection(e.g., a received signal strength beam quality metric, e.g., RSSI orRSRP or reference signal received quality (RSRQ)). If per block 1522multiple beam failure recovery request transmission attempts areunsuccessful, then per block 1524 the Radio Link Failure procedure isinitiated.

In order to allow flexible integration of beam management intoprocedures like RLM, RLF or link adaptation algorithms, a set ofconfigurable conditions will be beneficial to trigger different actionssuch as:

-   -   Beam switching,    -   Beam broadening/combining,    -   Fallback from a narrow beam to a wide beam, and    -   Beam failure recovery.

The actions are supported by various functionalities which areimplemented on either the gNB, the UE or can be common to both. Twospecific new functionalities to aid in optimal beam management andrecovery will be described shortly: a) Multiple threshold settings forbeam failure triggering, and b) Beam broadening.

Aspects of threshold setting for Beam Failure Triggering will now bedescribed. The following beam triggering process may robustly andefficiently handle multiple types of beam failure while minimizing thelatency of the beam recovery procedure. Support for multiple thresholdsfor the UE may be supported: a) Beam Switching threshold and b) Controlchannel beam failure threshold.

FIG. 16 is a diagram illustrating beam management and beam recovery. Thediagram includes a beam quality metric 1612 measured along a verticalaxis, with worse beam quality in the downward direction and better beamquality in the upward direction. A beam switching threshold 1614 and acontrol channel beam failure threshold 1616 are shown. The beamswitching threshold 1614 indicates a higher beam quality than thecontrol channel beam failure threshold 1616 and is used to trigger atleast the Type 1 beam failure. The control channel beam failurethreshold 1616 is used to trigger at least the Type 2 beam failure.Scenarios that might lead to beam failure may differ in terms of howfast and how severely the beam quality deteriorates. A trigger conditionconsists of a measurement metric related threshold and a timer for whichthe measurement metric violates the threshold. A set of at least twotrigger conditions that might have different thresholds and timers isdefined. The threshold and the timer of each of the trigger conditionsmay be reconfigured.

Aspects of beam broadening will now be described. The SS or the UESpecific CSI-RS may be used as the DL-RS for the PDCCH. The CSI-RS mayhave a narrow beam width and the SS may have a broad beam width. ThePDCCH may initially be QCL'ed with the SS until the P2/P3 beamrefinement procedure is performed and the UE can be configured with theUE specific CSI-RS.

A symmetric mechanism is to use the nested structure of multiple CSI-RSthat are QCLed with a SS beam to allow for a smooth recovery with lowlatency from a beam failure. For example, when a PDCCH that isconfigured with a narrow beam CSI-RS triggers a beam failure using thesecond threshold, the narrow beam is lost due to gradual motion orrotation. In this case, it is quite likely that the neighboring beamswill be good enough and broadening the beam that is serving the UE maybe considered. The SS within which the CSI-RS is nested may be used.

An example of the nested structure is shown in FIGS. 2A, 2B, 3A and 3B.When the PDCCH is associated with a UE Specific CSI-RS as its DL RS, itcan attempt to broaden its serving beam before proceeding with thenormal beam recovery process to reduce the beam recovery latency. Beambroadening is supported to reduce transmission of beam recoveryrequests.

Aspects of the various roles of the UE and gNB in beam management andrecovery will now be described. The beam recovery procedure may becontrolled by the gNB and the UE via setting the relevant configurablethresholds and timers. Alternative methods for setting up the thresholdsand timers at the gNB and the UE will now be described in which the beammanagement and recovery is controlled and initiated by the gNB or by theUE. First, beam management and recovery with UE assistance will bedescribed.

FIG. 17 (collectively FIGS. 17A and 17B) is a signal diagramillustrating a UE-initiated beam management method. In the UE-controlledmethod, the UE is the primary controller of the beam management andrecovery procedures, whereas the gNB configures the UE through L2/L3(Level 3) signaling. A UE in RRC_CONNECTED state may have the followingbeam management tasks.

First, the UE provides beam measurement reports to the gNB according tothe periodicity configured by the gNB. This includes appropriate beammeasurements on the set of active beams configured by gNB. The UE can beRRC configured by the gNB for a specific periodicity of the BeamMeasurement Report. The measurement metric may be the L1 RSRP on SSand/or UE Specific CSI-RS that have been configured by the gNB as theactive beam set.

Second, the UE may optionally initiate beam switching via the P2/P3 beamrefinement procedure based on its monitoring of the beam quality metricas described above with respect to FIG. 16. The UE may optionally selecta new RX beam as the outcome of the P3 procedure. This can be triggeredby the UE or by the gNB. The UE also initiates beam broadening whennecessary.

Third, the UE may initiate and signal Beam Failure triggering. The UEmay trigger a beam failure event via monitoring the beam quality of theserving beam for the DL RS used for beam management. The beam qualitymetric can be RSSI or SINR. A beam failure is triggered when the beamquality metric falls below a threshold and stays below the threshold fora period of time defined by a timer. The threshold setting and timervalues may be configured by the gNB via L2/L3 signaling.

As shown in FIG. 17, initially, the gNB signals the UE to configure thebeam reporting periodicity 1701, configure the beam failure thresholdsand timers 1703, configure the set of active beams 1705, and indicatethe TX beam 1707. Subsequently, the UE performs beam measurement on theSS 1709. The UE then determines whether the control channel beam hasbeen lost 1711. If so, beam recovery 1712 is performed. If not, the UEsends an SS beam measurement report to the gNB 1713. The UE alsoperforms beam measurement on CSI-RS 1715. The UE then determines whetherbeam switching is needed 1717. If not, the UE sends a CSI-RS beammeasurement report to the gNB 1719 and flow returns to 1709 in which theUE performs beam measurement on SS. Otherwise, UE TX beam refinement ofCSI-RS is performed according to P3 1721. Next, the UE determines againwhether beam switching is needed 1723. If not, the UE sends a CSI-RSbeam measurement report to the gNB with information indicating whetheror not the UE RX beam was changed 1725 and flow returns to 1709.Otherwise, the UE signals the gNB to request a TRP TX beam sweep onCSI-RS 1727. Subsequently, TRP TX beam refinement on CSI-RS is performedaccording to P2 1729, and the UE sends a CSI-RS beam measurement reportto the gNB 1731. The gNB defines a set of active beams, defines a beamreporting periodicity, defines beam failure thresholds and timers, andselects a TRP TX beam 1733. The gNB signals the UE to configure the beamfailure thresholds and timers 1735, configure the beam reportingperiodicity 1737, configure the set of active beams 1739, and indicatethe TX beam 1741. Next, the UE determines again whether beam broadeningis needed 1743. If not, flow returns to 1709. If so, the UE signals thegNB to request beam fallback to the TRP TX beam based on the SS 1745.Subsequently, based on SS beams, the gNB defines a set of active beamsand selects a TRP TX beam 1747. The gNB then signals the UE to configurethe beam failure thresholds and timers 1749, configure the beamreporting periodicity 1751, configure the set of active beams 1753, andindicate the TX beam 1755, and flow returns to 1709.

FIG. 18 (collectively FIGS. 18A and 18B) is a signal diagramillustrating a gNB-initiated beam management method. In thegNB-controlled method, the gNB is the primary controller of the beammanagement and recovery procedures, whereas the UE is configured by thegNB through L2/L3 signaling for the appropriate beam measurement andreporting settings. FIG. 18 illustrates a concise view of a beammanagement embodiment for a UE in CONNECTED state including howdifferent thresholds trigger different actions. The gNB may have thefollowing tasks for beam management of a UE in RRC_CONNECTED state.

First, the gNB configures UE Specific CSI-RS for each UE. Second, thegNB indicates the set of active beams and selected RX and TX beam to theUE through L2/L3 signaling. Third, the gNB configures Beam MeasurementSettings and Beam Reporting Settings. The gNB may configure periodicBeam Measurement reports from each UE. The periodicity may be configuredto be the same or different for every UE. In addition to the periodicBeam measurement reports, additional aperiodic beam measurement reportscan also be scheduled by the gNB. A Beam Measurement Report timer may beassociated with the reports with the largest timer value set to the timeinterval between two successive reports from a specific UE. Fourth, inpreemptive beam switching, the gNB can track the beam quality of theserving beam and other beams in the active beam set that are reported bythe UE in the beam measurement report. If a beam in the active set isbetter than the serving beam, the gNB may switch or broaden the servingbeam for the UE and signal the beam change. Fifth, the gNB may initiateP2/P3 procedure(s) for beam refinement. Sixth, Beam Failure triggeringmay be initiated by the gNB. The gNB may trigger a beam failure if 1)the reported serving beam quality is lower than a threshold for aspecific number of successive reports or 2) the Beam Measurement Reporttimer expires, i.e. the link was not good enough for UE to successfullyreceive the beam measurement configuration or send back the beammeasurement report.

As shown in FIG. 18, initially, the gNB signals the UE to configure thebeam reporting periodicity 1801, configure the beam failure thresholdsand timers 1803, configure the set of active beams 1805, and indicatethe TX beam 1807. Subsequently, the UE performs beam measurement on theSS 1809. The UE then determines whether the control channel beam hasbeen lost 1811. If so, beam recovery 1812 is performed. If not, the UEsends an SS beam measurement report to the gNB 1813. The UE alsoperforms beam measurement on CSI-RS 1815. The UE then sends a CSI-RSbeam measurement report to the gNB 1816. The gNB determines whether RXbeam switching is needed 1818. If not, the gNB flow returns to the stateafter 1807 in which the gNB waits for the UE to send an SS beammeasurement report. Otherwise, the gNB signals the UE to configure theUE for a CSI-RS based P3 procedure 1820. The UE performs UE RX beamrefinement according to P3 1822. The UE then sends a CSI-RS beammeasurement report 1824. The gNB then determines whether TX beamswitching is needed 1826. If not, the gNB signals the UE to indicate theRX beam 1828 and the gNB flow returns to the state after 1807.Otherwise, the gNB configures the UE for a CSI-RS based P2 procedure1832. TRP TX refinement on CSI-RS is then performed according to P21834. The UE then sends a CSI-RS beam measurement report to the gNB1836. The gNB then defines a set of active beams, defines a beamreporting periodicity, defines beam failure thresholds and timers, andselects a TRP TX beam 1838. The gNB then determines whether beambroadening is needed 1842. If not, the gNB signals the UE to configurethe beam reporting periodicity 1844, configure the set of active beams1846, and indicate the TX beam 1848, and the gNB flow returns to thestate after 1807. Otherwise, based on SS beams, the gNB defines a set ofactive beams and selects a TRP TX beam 1852. Then, the gNB signals theUE to configure the beam reporting periodicity 1854, configure the setof active beams 1856, and indicate the TX beam 1858, and the gNB flowreturns to the state after 1807.

Table 1 below summarizes various aspects of the roles of the UE and gNBin beam management and recovery. In particular, beam failure recoverymay be initiated by either the UE or gNB. In some cases, gNB-initiatedbeam failure recovery may lower recovery time.

TABLE 1 UE Controlled gNB Controlled Beam Failure UE triggers gNBtriggers Triggering Beam Failure Beam Failure Threshold to Configured atImplemented within gNB declare UE by gNB via and independent of the BeamFailure L2/L3 message UE Timer to Configured at Configured at gNB.declare UE by gNB via Implicitly set using Beam Failure L2/L3 messagenumber of successive Beam Reports Or explicit Beam Measurement Reporttimer implemented at gNB Latency to Medium to High (Timer Low to Medium(Beam recover from expiry period + reporting period + Beam Failure Waittill next PRACH Timer expiry period + window + Beam Recovery Beamresponse window) Request Response monitoring time)

It is noted that the techniques described herein can be used for massiveMIMO (multiple input, multiple output) cellular telecommunicationsystems such as those described in U.S. Published Patent Application2015/0326286, entitled “MASSIVE MIMO ARCHITECTURE,” U.S. PublishedPatent Application 2015/0326383, entitled “SYNCHRONIZATION OF LARGEANTENNA COUNT SYSTEMS,” and U.S. Published Patent Application2015/0326291, entitled “SIGNALING AND FRAME STRUCTURE FOR MASSIVE MIMOCELLULAR TELECOMMUNICATION SYSTEMS,” each of which is herebyincorporated by reference in its entirety. It is further noted thatdifferent and/or additional features can also be implemented, asdesired, and related systems and methods can be utilized as well. Suchmassive MIMO communication systems can be used for 5G dynamic TDD (timedivision duplex) air interfaces. The 5G (5^(th) generation) mobiletelecommunications system is able to span a wide variety of deploymentscenarios (e.g., Rural, Urban Macro, Dense Urban, Indoor, etc.) in aflexible and scalable manner. In particular, massive MIMOreciprocity-based TDD air interfaces allow for symbol-level switchingand potential configurability that in turn allow for features to supportthree primary aspects of 5G air interfaces, namely enhanced MobileBroadBand (eMBB), massive Machine Type Communications (mMTC) andUltra-Reliable and Low Latency Communications (URLLC).

It is still further noted that the functional blocks, components,systems, devices, and/or circuitry described herein can be implementedusing hardware, software, or a combination of hardware and software. Forexample, the disclosed embodiments can be implemented using one or moreprogrammable integrated circuits that are programmed to perform thefunctions, tasks, methods, actions, and/or other operational featuresdescribed herein for the disclosed embodiments. The one or moreprogrammable integrated circuits can include, for example, one or moreprocessors and/or PLDs (programmable logic devices). The one or moreprocessors can be, for example, one or more central processing units(CPUs), controllers, microcontrollers, microprocessors, hardwareaccelerators, ASICs (application specific integrated circuit), and/orother integrated processing devices. The one or more PLDs can be, forexample, one or more CPLDs (complex programmable logic devices), FPGAs(field programmable gate arrays), PLAs (programmable logic array),reconfigurable logic circuits, and/or other integrated logic devices.Further, the programmable integrated circuits, including the one or moreprocessors, can be configured to execute software, firmware, code,and/or other program instructions that are embodied in one or morenon-transitory tangible computer-readable mediums to perform thefunctions, tasks, methods, actions, and/or other operational featuresdescribed herein for the disclosed embodiments. The programmableintegrated circuits, including the one or more PLDs, can also beprogrammed using logic code, logic definitions, hardware descriptionlanguages, configuration files, and/or other logic instructions that areembodied in one or more non-transitory tangible computer-readablemediums to perform the functions, tasks, methods, actions, and/or otheroperational features described herein for the disclosed embodiments. Inaddition, the one or more non-transitory tangible computer-readablemediums can include, for example, one or more data storage devices,memory devices, flash memories, random access memories, read onlymemories, programmable memory devices, reprogrammable storage devices,hard drives, floppy disks, DVDs, CD-ROMs, and/or any othernon-transitory tangible computer-readable mediums. Other variations canalso be implemented while still taking advantage of the new framestructures described herein.

Further modifications and alternative embodiments of this invention willbe apparent to those skilled in the art in view of this description. Itwill be recognized, therefore, that the present invention is not limitedby these example arrangements. Accordingly, this description is to beconstrued as illustrative only and is for teaching those skilled in theart the manner of carrying out the invention. It is to be understoodthat the forms of the invention herein shown and described are to betaken as present embodiments. Various changes may be made in theimplementations and architectures. For example, equivalent elements maybe substituted for those illustrated and described herein, and certainfeatures of the invention may be utilized independently of the use ofother features, all as would be apparent to one skilled in the art afterhaving the benefit of this description of the invention.

1. A user equipment (UE) for performing radio frequency beam management in communication with a base station, comprising: a memory, configured to store a threshold; a processor, configured to: evaluate a beam quality metric against the threshold; switch from a first beam to a second beam in response to determining the beam quality metric falls below the threshold; transmit to the base station a report that includes beam measurements; and wherein the report indicates the UE has performed the switching and that the beam measurements are with respect to the second beam.
 2. The UE of claim 1, wherein the UE transmits the report on an uplink control channel.
 3. The UE of claim 2, wherein the uplink control channel is a Physical Uplink Control Channel (PUCCH).
 4. The UE of claim 1, wherein the UE transmits the report on an uplink shared channel.
 5. The UE of claim 4, wherein the uplink shared channel is a Physical Uplink Shared Channel (PUSCH).
 6. A method for performing radio frequency beam management in communication between a base station and a user equipment (UE), the method comprising: evaluating, by the UE, a beam quality metric against a threshold; switching from a first beam to a second beam in response to determining the beam quality metric falls below the threshold; transmitting, by the UE to the base station, a report that includes beam measurements; and wherein the report indicates the UE has performed said switching and that the beam measurements are with respect to the second beam.
 7. The method of claim 6, wherein said transmitting the report is performed by the UE on an uplink control channel.
 8. The method of claim 7, wherein the uplink control channel is a Physical Uplink Control Channel (PUCCH).
 9. The method of claim 6, wherein said transmitting the report is performed by the UE on an uplink shared channel.
 10. The method of claim 9, wherein the uplink shared channel is a Physical Uplink Shared Channel (PUSCH).
 11. A base station (BS)/user equipment (UE) attempting to pre-empt radio frequency beam failure in communication between a UE/BS, comprising: a memory, configured to store a threshold; a processor, configured to: associate narrower and broader beams between the BS and the UE; use the narrower beam, rather than the broader beam, to transfer user data between the BS and the UE; evaluate a beam quality metric of the narrower beam against the threshold; and switch to using the broader beam, rather than the narrower beam, to transfer user data between the BS and the UE in response to determining the beam quality metric of the narrower beam falls below the threshold.
 12. The BS/UE of claim 11, wherein the processor is further configured to: construct a first beam set of wide beam reference signals (RS) each having a direction and a width, wherein the direction of each wide beam RS is unique from the others in the first beam set; construct a second beam set of narrow beam RS each having a direction and a width, wherein the direction of each narrow beam RS is unique from the others in the second beam set and the width of the narrow beam RS is narrower than the width of the wide beam RS; wherein each narrow beam RS of the second beam set is uniquely linked to a wide beam RS of the first beam set according to a linkage; wherein the direction of each narrow beam RS is spatially nested within the width of the wide beam RS to which it is uniquely linked; and wherein the associated narrower and broader beams are of the second and first beams sets, respectively, and are uniquely linked according to the linkage.
 13. The BS/UE of claim 12, further comprising: wherein during a beam management process, the UE receives and selects one of the narrow beam RS of the second set as a strongest measured narrow beam RS, and the UE correspondingly selects the wide beam RS to which the strongest measured narrow beam RS is uniquely linked according to the linkage.
 14. The BS/UE of claim 13, further comprising: wherein when the narrow beam RS is selected for the UE, the broad beam RS that is uniquely linked to the selected narrow beam RS is explicitly indicated as part of a narrow beam configuration message sent to the UE by the BS.
 15. The BS/UE of claim 12, further comprising: wherein the linkage is indicated to the UE implicitly.
 16. A method for attempting to pre-empt radio frequency beam failure in communication between a base station (BS) and a user equipment (UE), the method comprising: associating narrower and broader beams between the BS and the UE; using the narrower beam, rather than the broader beam, to transfer user data between the BS and the UE; evaluating a beam quality metric of the narrower beam against a threshold; and switching to using the broader beam, rather than the narrower beam, to transfer user data between the BS and the UE in response to determining the beam quality metric of the narrower beam falls below the threshold.
 17. The method of claim 16, further comprising: constructing, by the BS, a first beam set of wide beam reference signals (RS) each having a direction and a width, wherein the direction of each wide beam RS is unique from the others in the first beam set; constructing, by the BS, a second beam set of narrow beam RS each having a direction and a width, wherein the direction of each narrow beam RS is unique from the others in the second beam set and the width of the narrow beam RS is narrower than the width of the wide beam RS; wherein each narrow beam RS of the second beam set is uniquely linked to a wide beam RS of the first beam set according to a linkage; wherein the direction of each narrow beam RS is spatially nested within the width of the wide beam RS to which it is uniquely linked; and wherein the associated narrower and broader beams are of the second and first beams sets, respectively, and are uniquely linked according to the linkage.
 18. The method of claim 17, further comprising: wherein during a beam management process, the UE receives and selects one of the narrow beam RS of the second set as a strongest measured narrow beam RS, and the UE correspondingly selects the wide beam RS to which the strongest measured narrow beam RS is uniquely linked according to the linkage.
 19. The method of claim 18, further comprising: wherein when the narrow beam RS is selected for the UE, the broad beam RS that is uniquely linked to the selected narrow beam RS is explicitly indicated as part of a narrow beam configuration message sent to the UE by the BS.
 20. The method of claim 17, further comprising: wherein the linkage is indicated to the UE implicitly. 